1. Field of the Invention:
The present invention relates to an improvement in a device for driving the copy board of a copying machine.
2. Description of the Prior Art:
The copy board driving device of a conventional copying machine having a reciprocating copy board has a driving member which is unitarily connected to the reciprocative copy board and adapted to move reciprocatively together with the latter. When an external force which would prevent the reciprocative movement is applied to the copy board, the driving force is conveniently absorbed by clutch means, such as a friction clutch or the like, incorporated in a transmission system, so that the driving device may be protected against any damaging force.
Since it is not permissible to cause a phase differential between the copy board and its associated members, the clutch means is disposed at the power-side so that coincidence of phase may be achieved easily. Therefore, the clutch means is required to transmit a large torque for driving not only the copy board but also the other moving parts such as a photosensitive drum and a paper-feeding device. Therefore, the safety function or slipping in the clutch means is not achieved unless a very large external force is applied to the copy board. Alternatively, the clutch means is required to exhibit highly precise operation. If the clutch means is mounted on the same side as the reciprocative driving member, a complicated mechanism is required for matching the phase of the copy board and its associated members.
Further, in a known type of copying machine the reciprocating copy board extends out of the copying machine body when the power switch is turned on. The copy board is capable of being stored in the copying machine body without projecting therefrom when in operative condition. This is preferred in consideration of designing a compact machine. In such a machine, if it is used in confined office space and the copy board projects into an aisle during a copying operation, it will become an obstacle to workers moving in the aisle. Therefore, it is desirable that the copy board be retracted into the machine body. However, it is troublesome to do so in the case in which a clutch is mounted on the power side of the driving member, as mentioned above, since it has to be operated after the power switch is turned off. Besides, when the copying operation is started from this condition after the power switch is turned on, the first copy comes to nothing, because matching of the phase of the copy board, rotation of the photosensitive member, the sheet supplying operation and so forth cannot be achieved on the first copying operation.